´óÏó´«Ã½

It would be reassuring to think that the world's worst nuclear disaster since Chernobyl is contained, and the Fukushima Daiichi nuclear power plant is in stable shut-down.

Unfortunately a look inside the Fukushima plant suggests otherwise.

I was part of a group taken in to the Fukushima plant last week, only the second time foreign TV journalists have been allowed in since the disaster two year ago. Very little that we saw in our brief two-hour tour was reassuring.

Our first stop was reactor building number four. This place was potentially the most worrying.

Inside the shattered building, more than 1,500 spent fuel rods were still sitting inside a cooling pool. They were still highly radioactive and the pool was outside the reactor's steel and concrete containment vessel, perched high on the third floor.

A race is now on to get the fuel rods out. A huge steel structure is being erected around building four that will be used to raise the spent fuel out.

But that operation will not start until the end of this year, and will then take two more years to complete. If another large earthquake strikes during that time there is real concern the building could collapse.

Tepco, the company that runs the plant, told us the building was now strong enough to withstand another quake. But contractors who have worked inside building four have reported that the structure is still extremely fragile.

Reactor number four was only the tip of a radioactive iceberg. Two hundred meters away I could clearly see the twisted and rusting steel of reactor building number three.

Two years after the disaster it was still virtually untouched. The reason was simple. The radiation at reactor three was so high workers could not safely go near it.

Our bus rushed past without stopping. The Geiger counter reading was over 1,000 micro sieverts an hour. That is roughly the same as ten chest X-rays every hour, or a full CT scan every ten hours.

Like reactor four, reactor three had spent fuel rods sitting inside a cooling pool beneath the twisted steel and rubble. Remotely-operated cranes are being used to try and pull away the debris, but it is a painfully slow process.

Tepco's other huge problem is contaminated water, tens of thousands of tonnes of it.

The 9.0 earthquake that struck two years ago appears to have severely damaged the foundations of the plant - creating large cracks in the underground walls that are supposed to keep the plant water tight.

Ground and seawater is now leaking through the cracks in to the basements around the reactors.

The water rapidly becomes highly contaminated and cannot be pumped out into the sea. Instead Tepco is building huge 1,000 tonne water tanks to store the contaminated water.

The Fukushima site is now dotted with hundreds of them. But the water leakage is so severe that they are having to add a new tank every two to three days. Within two years they will have run out of room.

At the end of our tour we were given 10 minutes with the plant manager, Takeshi Takahashi. Mr Takahashi looked exhausted, dark rings around his eyes.

After a long apology for the "inconvenience" caused by the nuclear disaster, Mr Takahashi explained just how long and difficult the clean up would be.

"We need to remove the broken and damaged fuel and safely isolate it. This work will take 30 to 40 years. Even during the process we should never release any radioactive material into the surrounding environment."

It would be easy for an outsider like me to criticise him: why were they not working faster? Why did they still not know what was going on inside the melted-down reactors?

But the truth is no-one would wish a job like Mr Takahashi's on their worst enemy. No one has ever dealt with a situation like this before. He and his 3,000 staff are venturing in to completely uncharted territory.

And, according to most observers, they are, after a poor start, doing most things right.

But the scale of their task is daunting, and it will decades before anyone can truly say the Fukushima disaster is over, and the threat from the plant contained.